As of fact. In the Sensory-Illusion argument, Descartes argues

As technology and science advanced, people eventually came to seek more answers as to how the world around them worked, people sought to answer the spiritual and intangible aspects of reality and wished to understand what exactly made something knowledge. As people became more and more curious eventually a field of philosophy called Epistemology appeared, which sought to find out the method through which we, as human beings, acquired and used knowledge in our daily lives. Two of the main subsets of this field were Rationalism and Empiricism, with some of the main figures in both being Descartes and Hume respectively. While we could say that both Hume and Descartes sought answers as to how human beings gain knowledge, they both had different approaches and ideas as to how it’s gained. At their roots, both epistemological subsets sought to find answers to things that people had previously attributed to factors such as a higher power, the soul, and the other more spiritual aspects of life. Both sought the answer to the age-old question, why people thought and believed the things that they did and how these things influenced their lives.René Descartes was a key figure of Rationalism, with one of the main points in his works being the “method of doubt”, the idea that we cannot be certain of anything which may have the slightest possibility of being incorrect. In order to be certain of anything, it must be irrefutable from any and every viewpoint. Descartes deemed certainty of the utmost importance, deeming certainty to be of the highest status, followed by knowledge and then lastly by beliefs or opinions. To Descartes, the only thing that was certain pertaining to humanity and himself was that he was a “thinking thing”. Descartes sought to base knowledge on tangible truths, rather than “what ifs” or other uncertainties, he was more concerned with “a posteriori” —matters of fact. In the Sensory-Illusion argument, Descartes argues that since his senses have deceived him in the past, for all he knows it’s very possible that his senses always deceive and that his sense-based beliefs are all false. This argument laid the basis for some of Descartes’ other arguments as well, such as the Dreaming Argument, in which he argues that it’s possible that we are living in a dream, seeing as how there are no reliable signs through which we can distinguish between the living and dreaming worlds. The Dreaming Argument shows us the attitude of skepticism (also known as Cartesian doubt) that Descartes wanted us to adopt in our pursuit of knowledge and truth, despite how outlandish it may seem at first glance. “I will set aside anything that admits of the slightest doubt, treating it as though I had found it to be outright false; and I will carry on like that until I find something certain, or, at worst, until I become certain that there is no certainty. (Descartes 4)Descartes also believed that humans are born with innate (a priori) knowledge when it came to common question of humanity such as the existence of a higher power and the soul. Descartes goes so far as to prove the existence of God through a priori knowledge reinforced by reasoning in his fifth mediation. “The very fact that I, an incomplete and dependent being have an image of an independent and perfect being in my mind means that God exists and that every moment of my existence depends on him.” (Descartes 18)On the other side of Epistemology we had David Hume, a leading figure of Empiricism who argued that true knowledge is ultimately impossible to attain. Since our knowledge is obtained from sensory experience and colored by our perceptions, it’s impossible for two human beings to think in the same way as well, contradicting Descartes’ belief which argued that human beings were innately similar when it came to things such as their thoughts and beliefs. Descartes believed that human beings had innate ideas when it came to three things, which were the self, substance, and God. On the other hand, Hume argued that knowledge is acquired from the senses and also believed that we are born with a blank slate (tabula rasa). Our experiences allow us to obtain knowledge in the world—knowledge which is then influenced by our perceptions of the world around us and of our lives. These perceptions allow causation to occur, which allows us to make comparisons between two seemingly unrelated things. This causation develops through life experience. “Nothing at first view may seem more unbounded than the thought of man, which not only escapes all human power and authority, but is not even restrained within the limits of nature and reality. To form monsters, and join incongruous shapes and appearances costs the imagination no more trouble than to conceive the most natural and familiar objects.” (Hume 1)Hume also makes a point of stating in his works that the conclusions that we draw from our perceptions may not always be true. Although we may be convinced that something is true it may only be true to us. What we perceive may not necessarily be true because of factors such as our emotional state or what we have experienced in life. For instance, someone who has lived their whole life being in an abusive household may think that humans are inherently abusive and cruel. “While the body is confined to one planet, along with it creeps pain and difficulty, the thought can in an instance transport us…into the unbound chaos. What never was seen, or heard of, may yet be conceived; nothing is beyond the power of thought.” (Hume 2)Overall we could say that Descartes is more theologically minded, Descartes sought to break down things to the root and discover intangible spiritual truths that everyone could undoubtedly agree with, similar famous theological figures such as St. Thomas Aquinas. Descartes believed that at the end of the day, human beings were fundamentally the same at the core, so they could all agree on ideas once they had been broken down enough. At the same time, Descartes incorporated mathematics into his works, saying that the universe was mathematically logical and that everything could be proven through reasoning. Hume closely resembles a modern-day psychologist, since he goes into detail about how our perceptions color our knowledge of the world, which is closely related to modern-day cognitive science, which is a mixture of the fields of the fields of psychology, philosophy, and anthropology. Cognitive science goes into great depth pertaining to things such as our beliefs and thought patterns. In a way we could say that Hume was one of the leading pioneers of modern-day cognitive science. We could also say that Hume has more Atheist tendencies, since he argues that knowledge can only be obtained through the senses, invalidating the possible existence of a God seeing as intangible things cannot be experienced by the senses, While Descartes was more scientifically minded (seeing as he was a mathematician as well) we could say that Descartes was also quite ironically more spiritual, since Descartes uses logic and reason to solve the intangible aspects of life, such as the existence of a higher power. Despite these differences, we could say that both Descartes and Hume we in a way similar. Both sought the answer as to how people went about collecting knowledge and what exactly knowledge was . Both Rationalism and Empiricism fell under epistemology, just with different nuances. At the end of the day both are two sides of the same coin.